NCIS Two of Gibbs' (Mark Harmon) ex-wives (Melinda McGraw and Jeri Ryan) show up at a crime scene, and team members are intrigued by the ex-wife they've never met in this new episode. 8 p.m. CBS

MasterChef A new cohort of young chefs shows off its cooking skills in the season premiere of the third "MasterChef Junior." Joe Bastianich (who plans to leave the franchise soon) and Graham Elliot join Gordon Ramsay on the judging panel. 8 p.m. Fox

Pretty Little Liars The winter season of this teen thriller opens with a new episode that picks up from the action three months after viewers last saw Alison, Paige, Emily (Sasha PieterseLindsey Shaw, Shay Mitchell) and the rest of the characters. 8 and 10 p.m. Family

Switched at Birth The family learns about Bay's (Vanessa Marano) decision to take the blame for Daphne's (Katie Leclerc) illegal actions in the season premiere. 9 p.m. Family

About a Boy One year after Will and Marcus (David Walton and Benjamin Stockham) became friends, they celebrate their "manniversary" at a music festival, where they see Lisa Loeb (herself) in this new episode. 9:30 p.m. NBC

Forever When the son of a fellow-military-veteran friend of Abe's (Judd Hirsch) is found dead, Henry and Jo (Ioan Gruffudd, Alana De La Garza) investigate, unaware that Abe and pals from his Army days are also investigating. William Baldwin guest stars in this new episode. 10 p.m. ABC

Frontline The National Rifle Assn. is in the spotlight in the new episode "Gunned Down," which examines the influence it has over gun regulation in the United States. 10 p.m. KOCE

Framework Common ("Hell on Wheels") hosts a furniture designing and building competition in this new series. 10 p.m. Spike

Child Genius In this new series, hosted by former astronaut Leland Melvin, 20 smart kids between the ages of 8 and 12 compete to win a $100,000 college fund prize. 10 p.m. Lifetime